JP2005120971A - Control device for secondary air supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize stable operation of an engine while actualizing purifying exhaust gas in a secondary air supply system intended to purify exhaust gas. <P>SOLUTION: This control device comprises a step S100 of detecting the combustion condition of the engine from a change in the speed of the engine and a step S400 of determining that secondary air supplied to an exhaust pipe flows back to a cylinder chamber to make a combustion air-fuel ratio lean when the combustion of the engine is instable (YES in S200) and of stopping the supply of the secondary air or restricting the supply amount of the secondary air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust purification technology for an exhaust system of an internal combustion engine, and more particularly to a control device for a secondary air supply system that supplies secondary air upstream of an exhaust purification device.

  2. Description of the Related Art As an exhaust gas purification device for an internal combustion engine, a device that arranges a catalyst in an exhaust system and purifies CO, HC, NOx components, etc. in exhaust gas is known. Furthermore, secondary combustion of HC and CO in the exhaust gas is performed by supplying secondary air into the exhaust pipe through a secondary air supply passage having an on-off valve connected to the exhaust pipe to increase the oxygen concentration. A technique for promoting exhaust gas purification is known.

  In such a case, part of the secondary air supplied to the exhaust pipe due to the exhaust pulsation flows into the combustion chamber, the combustion air-fuel ratio becomes lean, the engine combustion becomes unstable, and drivability (Such as poor idling, hesitation, engine stall, etc.) may occur. In relation to such problems, there is a technique disclosed in the following publications.

  Japanese Utility Model Laid-Open No. 5-58817 (Patent Document 1) purifies and silences exhaust gas while storing an oxidation catalyst in an engine muffler and preventing secondary air from flowing back into the cylinder chamber with a simple structure. Disclosed is a device for purifying and silencing exhaust gas of a mixture-air intake type engine, which reduces the size of the engine by reducing the size of the device. This exhaust gas purification / silencer for an air-fuel mixture type engine communicates an oxidation catalyst and a muffler with the exhaust port of the air-fuel mixture type engine, and the exhaust gas purification system is connected to an exhaust gas passage upstream of the oxidation catalyst. A device for purifying and silencing exhaust gas of a mixed-air intake type engine configured to communicate with a secondary air supply path for the engine, wherein a catalyst chamber is formed downstream of the primary silencing chamber in the muffler body of the muffler, An oxidation catalyst is accommodated in the catalyst chamber, facing the primary silencing chamber, the exhaust inlet hole and the outlet of the secondary air supply path are opened, and the outlet of the secondary air supply path and the exhaust gas are opened in the primary silencing chamber. The secondary air suction prevention plate is interposed between the inlet hole and the secondary air supplied from the outlet of the secondary air supply path by the pulsation of the exhaust pressure in the primary silencing chamber. Secondary air sucking out that is short-circuited to And configured to prevent at stop plate.

  According to the exhaust gas purification / silencer device of the air-fuel mixture type engine, the secondary air is sucked into the muffler primary silencing chamber 8 from the outlet of the secondary air supply passage at the negative pressure portion of the engine exhaust pressure pulsation. It is. Since this secondary air is bypassed by the secondary air suction prevention plate and given ventilation resistance, it reaches the exhaust inlet hole, so that the amount of backflow to the cylinder chamber is greatly reduced. As a result, the air-fuel mixture having an appropriate concentration in the cylinder chamber is diluted by mixing with the secondary air, and the degree of difficulty in combustion is greatly reduced, and the amount of HC / CO generated in the cylinder chamber is reduced.

  Japanese Laid-Open Patent Publication No. 5-71336 (Patent Document 2) discloses an exhaust pipe air introduction device for an internal combustion engine that increases the efficiency of exhaust gas purification by controlling the amount of air introduced into the exhaust pipe of the internal combustion engine to an optimum value. To do. The exhaust pipe air introducing device of the internal combustion engine includes air amount control means for changing the amount of air to be introduced at an arbitrary time interval and / or arbitrarily setting the magnitude of the change in the amount of air to be introduced.

  According to the exhaust pipe air introduction device of the internal combustion engine, the change in the air quantity introduced into the exhaust pipe adjusted by the air quantity control means introduces the optimum air quantity according to the catalyst, and the exhaust pipe / catalyst exhaust gas. The gas purification action can be efficiently promoted.

  Japanese Patent Application Laid-Open No. 56-9618 (Patent Document 3) discloses that a part of the air supplied to the exhaust pipe at the time of overlap at the end of the exhaust stroke flows backward into the combustion chamber when the engine is under a low load, and the air-fuel mixture in the combustion chamber. A four-stroke multi-cylinder engine is disclosed that avoids destabilizing and destabilizing combustion. In this four-stroke multi-cylinder engine, a secondary air passage having a check valve is connected to an exhaust passage led from a combustion chamber so that the atmosphere is introduced into the exhaust using pulsation of exhaust pressure. A throat that is directed from the vicinity of the intake valve of the intake passage to a position that is biased to one side from the cylinder axis in the combustion chamber is provided, and the throat of each intake passage is communicated with each other by a sub-passage that extends to the throat.

According to this four-stroke multi-cylinder engine, during low-load operation of an engine in which a large amount of air flowing into the exhaust passage flows back into the combustion chamber, a thin and high-speed intake air flows around the cylinder core through the throat. It becomes a swirling high-speed vortex and promotes its combustion.
Japanese Utility Model Publication No. 5-58817 JP-A-5-71336 Japanese Patent Laid-Open No. 56-9618

  However, the above-described patent documents also have the following problems. In the exhaust gas purification / silencer disclosed in Patent Document 1, a secondary air suction prevention plate must be newly provided in the primary silencer chamber. The exhaust pipe air introduction device disclosed in Patent Document 2 promotes purification of exhaust gas by changing the amount of secondary air supplied to the exhaust pipe at an arbitrary time interval or arbitrarily setting the amount of air. Only. Therefore, for example, if the secondary air supply interval is set short or the amount of secondary air is set large, the secondary air may flow back into the cylinder chamber of the engine, and combustion is performed in a lean state. The problem cannot be solved. In the engine disclosed in Patent Document 3, it is necessary to provide a spout for improving the flame propagation property by using the reverse flow as a high-speed vortex as a countermeasure against the reverse flow of the secondary air into the cylinder chamber particularly at low load.

  Even if such disclosed technology is used, it cannot be avoided accurately that a part of the secondary air flows into the combustion chamber, the combustion air-fuel ratio becomes lean, and the combustion of the engine becomes unstable. In particular, engine combustion may become more unstable due to the influence of fuel properties, valve deposits, ignition system abnormality, and the like.

  The present invention has been made to solve the above-described problems, and its purpose is to achieve stable operation of the engine while realizing exhaust purification in a secondary air supply system for exhaust purification. It is to provide a control device.

  A control device according to a first aspect of the invention controls a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device of an exhaust system of an internal combustion engine. The control device includes detection means for detecting a combustion state in the internal combustion engine, and control means for controlling the supply of secondary air based on the detected combustion state.

  According to the first invention, if the combustion state in the internal combustion engine is unstable, for example, it is considered that the combustion air-fuel ratio becomes lean and the combustion becomes unstable. The secondary air supply device is controlled so as to limit the amount. As a result, leaning of the combustion air-fuel ratio is suppressed, so that combustion instability of the engine is eliminated, and deterioration of drivability and deterioration of exhaust emission due to poor combustion due to leaning of the combustion air-fuel ratio can be prevented. . On the other hand, if the combustion state in the internal combustion engine is not unstable, for example, the secondary air is supplied to the exhaust pipe upstream of the exhaust purification device, and the secondary combustion of HC and CO in the exhaust is promoted to purify the exhaust. At the same time, the exhaust temperature is increased to promote the temperature increase of the three-way catalyst of the exhaust purification device, thereby suppressing the deterioration of exhaust emission. As a result, it is possible to provide a control device that achieves stable engine operation while realizing exhaust purification in a secondary air supply system for exhaust purification.

  A control device according to a second aspect of the invention controls a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device of an exhaust system of an internal combustion engine. The control device includes a detection unit for detecting a combustion state predicted in the internal combustion engine, and a control unit for controlling the supply of secondary air based on the predicted combustion state.

  According to the second invention, when it is predicted that the combustion state in the internal combustion engine becomes unstable, for example, the secondary air supply device is controlled so as to prohibit or restrict the supply of the secondary air. . This prevents leaning of the combustion air-fuel ratio, thereby eliminating the factors that make the engine combustion unstable, and exhaust emissions due to poor drivability and poor combustion due to leaning of the combustion air-fuel ratio. Can be prevented. On the other hand, if the combustion state in the internal combustion engine is not predicted to be unstable, for example, secondary air is supplied to the exhaust pipe upstream of the exhaust purification device, and promotes secondary combustion of HC and CO in the exhaust. While purifying the exhaust gas, the exhaust gas temperature is raised to promote the temperature rise of the three-way catalyst of the exhaust gas purification device, thereby suppressing the deterioration of the exhaust emission. As a result, it is possible to provide a control device that realizes stable engine operation while achieving exhaust purification in a secondary air supply system for exhaust purification.

  In the control device according to the third invention, in addition to the configuration of the first or second invention, the detecting means includes means for detecting that the combustion state is unstable.

  According to the third aspect of the invention, the combustion of the exhaust pipe internal combustion engine is unstable because the air supplied to the exhaust pipe upstream of the exhaust purification device flows backward into the combustion chamber and the fuel air-fuel ratio becomes lean. Therefore, the secondary air supply device can be controlled.

  In the control device according to the fourth aspect of the invention, in addition to the configuration of the first aspect, the detection means includes means for detecting that the combustion state is unstable based on the rotational speed of the internal combustion engine. .

  According to the fourth invention, when the rotational speed of the internal combustion engine decreases or fluctuates, it is determined that the combustion of the internal combustion engine is unstable, and the supply of secondary air can be stopped or limited.

  In the control device according to the fifth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, the detection means is means for detecting that the combustion state is unstable based on a decrease in the rotational speed of the internal combustion engine. including.

  According to the fifth aspect of the invention, it is possible to detect that the combustion state is unstable based on the decrease in the rotational speed of the internal combustion engine.

  In the control device according to the sixth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, the detection means is means for detecting that the combustion state is unstable based on fluctuations in the rotational speed of the internal combustion engine. including.

  According to the sixth aspect of the present invention, it is possible to detect that the combustion state is unstable based on the change in the rotational speed of the internal combustion engine.

  In the control device according to the seventh aspect of the invention, in addition to the configuration of the second aspect of the invention, the detecting means detects that the predicted combustion state is unstable based on the fuel component supplied to the internal combustion engine. Means for doing so.

  According to the seventh aspect of the invention, it is possible to predict that the combustion state is unstable based on the degree of heavyness representing the fuel component supplied to the internal combustion engine.

  In the control device according to the eighth invention, in addition to the configuration of any one of the first to seventh inventions, the control means is arranged so that the supply amount of the secondary air decreases when the combustion state is unstable. Means for controlling.

  According to the eighth invention, the fact that the combustion state in the internal combustion engine is unstable means that the combustion air-fuel ratio becomes lean and the combustion becomes unstable, so the supply amount of secondary air is reduced. Thus, the secondary air supply device is controlled. Thereby, leaning of the combustion air-fuel ratio is suppressed, so that combustion instability of the engine is eliminated.

  In the control device according to the ninth invention, in addition to the configuration of any one of the first to seventh inventions, the control means changes the supply amount of the secondary air based on the degree of instability of the combustion state. Means for.

  According to the ninth aspect, the secondary air supply device can be controlled so as to reduce the supply amount of the secondary air in accordance with the degree of instability of the combustion state in the internal combustion engine.

  In addition to the configuration of any one of the first to ninth inventions, the control device according to the tenth invention includes means for detecting an abnormality related to the internal combustion engine, and if an abnormality is detected, And means for controlling the supply to stop or to reduce the supply amount.

  According to the tenth invention, when various sensors provided for controlling the internal combustion engine detect an abnormality, the supply of secondary air is controlled to be stopped or the supply amount is reduced. In this way, it is unclear whether the internal combustion engine is in an unstable state when the sensor is abnormal, so stop supplying the secondary air or reducing the supply amount so that the fuel air-fuel ratio does not become lean. It is possible to prevent the internal combustion engine from becoming unstable.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 shows an overall configuration of an engine and its peripheral devices including a control device for a secondary air supply system according to an embodiment of the present invention. The secondary air supply device 10 is attached to a multi-cylinder gasoline engine (hereinafter simply referred to as an engine) 20 that is an internal combustion engine. An intake pipe 200 and an exhaust pipe 210 are attached to the engine 20. A throttle 240 is disposed in the intake pipe 200 and is connected to the intake filter 250. Between the intake filter 250 and the throttle 240, an air flow meter 260 for measuring the air amount (primary air amount) and an intake air temperature sensor 270 for measuring the intake air temperature are arranged.

  The engine 20 is provided with an engine speed sensor 280 for measuring the engine speed. An engine ECU (Electronic Control Unit) 2000 that controls the engine 20 includes an output signal of an engine cooling water temperature sensor (not shown) in addition to the air flow meter 260, the intake air temperature sensor 270, and the engine speed sensor 280, and the opening degree of the throttle 240. Etc. are input.

An exhaust purification device 220 made of a three-way catalyst is disposed downstream of the exhaust pipe 210. O ₂ sensors 310 and 320 for detecting the oxygen concentration in the exhaust are disposed both upstream and downstream of the exhaust purification device 220. In place of the O ₂ sensor, an air-fuel ratio (A / F) sensor or a linear O ₂ sensor may be used.

The secondary air supply device 10 includes a secondary air supply passage 110 that connects a position between the intake filter 250 and the throttle 240 of the intake pipe 200 and the engine 20 and the upstream O ₂ sensor 310 of the exhaust pipe 210. Prepare. In the secondary air supply passage 110, an electric motor driven air pump (AP) 120, an air switching valve (ASV) 130, and a reed valve (RV) 140 as a check valve are arranged from the intake pipe 200 side. A pressure sensor 150 is disposed between the AP 120 and the ASV 130. A pipe 160 extending from the downstream side of the throttle 240 of the intake pipe 200 is connected to the ASV 130, and an electromagnetic valve 170 is further disposed on the pipe 160.

A control device 1000 that controls the operation of the secondary air supply device 10 is connected to the engine ECU 2000 so as to communicate information with each other. Further, the output signals of the pressure sensor 150 and the O ₂ sensors 310 and 320 are input, and the motor driving of the AP 120 and the opening and closing of the electromagnetic valve 170 are controlled. Control device 1000 may be configured by engine ECU 2000.

  In a state where the combustion of the engine 20 is stable, the secondary air supply device 10 opens the electromagnetic valve 170 so that the negative pressure in the intake pipe 200 is guided to the ASV 130 and the ASV 130 is controlled to open. At the same time, by driving the air pump 120, a part of the air that has passed through the air filter 250 is guided into the exhaust pipe 210 through the secondary air supply passage 110. At this time, control may be performed so that the amount of air guided to the exhaust pipe 210 is increased based on the degree of stable combustion of the engine 20.

  On the other hand, when it is predicted that the combustion of the engine 20 is not stable or no longer stable, the control device 1000 closes the electromagnetic valve 170 to close the ASV 130 and stops the air pump 120. Part of the air that has passed through the air filter 250 is prevented from being guided into the exhaust pipe 210 via the secondary air supply passage 110. At this time, control may be performed so that the amount of air guided to the exhaust pipe 210 is reduced based on the degree to which the combustion of the engine 20 is not stable.

  The air introduced into the exhaust pipe 210 increases the oxygen concentration in the exhaust gas, increases its A / F, and promotes secondary combustion of the HC and CO in the exhaust gas in the exhaust pipe 210 to purify the exhaust gas. Plan. Further, the exhaust temperature is increased to promote the temperature increase of the three-way catalyst of the exhaust purification device 220, thereby suppressing the deterioration of exhaust emission. In place of the combination of the ASV 130 and the electromagnetic valve 170, an electromagnetic valve can be used directly for the portion of the ASV 130.

  With reference to FIG. 2, a control structure of a program executed by control device 1000 will be described.

  In step (hereinafter, step is referred to as S) 100, control device 1000 detects the combustion state of engine 20. At this time, control device 1000 detects that the combustion state of engine 20 is unstable due to a decrease in engine speed measured by engine speed sensor 280 and a change in engine speed. When detecting that the combustion state of engine 20 is unstable, control device 1000 sets, for example, an engine combustion unstable flag from 0 to 1.

  In S200, control device 1000 determines whether or not it is detected that combustion of engine 20 is unstable. For example, if the engine combustion unstable flag is set to 1, it is determined that the combustion of the engine 20 is unstable. If it is not determined that combustion of engine 20 is unstable (NO in S200), the process proceeds to S300. If not (YES in S200), the process proceeds to S400.

  In S300, control device 1000 permits the supply of secondary air because it has not been determined that combustion of engine 20 is unstable.

  In S400, control device 1000 determines that combustion of engine 20 is unstable, and therefore prohibits or restricts the supply of secondary air.

  The operation of the control device for the secondary air supply system according to the embodiment of the present invention based on the above-described structure and flowchart will be described.

  While the vehicle is traveling, the control device 1000 detects the combustion state of the engine 20. At this time, the engine speed measured by the engine speed sensor 280 is compared with a predetermined engine speed reduction threshold value or engine speed fluctuation threshold value indicating that the combustion is unstable. Thus, the combustion state of the engine 20 is detected.

  If combustion in engine 20 is not unstable (NO in S200), secondary air is supplied (S300). The supplied secondary air increases the oxygen concentration in the exhaust gas, raises its A / F, promotes secondary combustion in the exhaust pipe 210 of HC and CO in the exhaust gas, purifies the exhaust gas, and exhaust temperature To increase the temperature of the three-way catalyst of the exhaust purification device 220, thereby suppressing the deterioration of exhaust emission.

  If combustion in engine 20 is unstable (YES in S200), the supply of secondary air is stopped or restricted (S400). Since leaning of the combustion air-fuel ratio is suppressed, instability of combustion of the engine 20 is eliminated, and deterioration of drivability and exhaust emission due to poor combustion due to leaning of the combustion air-fuel ratio can be prevented.

  As described above, according to the control device for the secondary air supply system according to the present embodiment, the combustion state of the engine is detected, and if the combustion of the engine is unstable, the secondary air to the exhaust pipe is Prohibit or restrict supply. For this reason, since leaning of the combustion air-fuel ratio is suppressed, combustion instability of the engine 20 is eliminated. On the other hand, if the combustion of the engine is not unstable, secondary air is supplied to the exhaust pipe, and the secondary combustion of HC and CO in the exhaust is promoted to purify the exhaust and promote the temperature rise of the three-way catalyst Reduces deterioration of exhaust emissions.

  In S100 of FIG. 2, the current combustion state of the engine 20 is not detected, but the future combustion state of the engine 20 is predicted, and it is determined that the predicted combustion state of the engine 20 is not unstable. (NO in S200), the process proceeds to S300, and if it is determined that the predicted combustion state of engine 20 is unstable (YES in S200), the process proceeds to S400. Also good. In this case, for example, the content (heavyness) of the polymer hydrocarbon contained in gasoline as the fuel is detected, and the future combustion state of the engine 20 is predicted based on this heavyness.

  Further, in S100 of FIG. 2, the degree of instability of engine combustion is calculated based on the degree of decrease in engine speed and the fluctuation in engine speed, and the exhaust pipe 200 is determined in accordance with the degree of instability. The amount of air supplied to the air may be controlled. At this time, the control device 1000 may control the driving state of the air pump 120 to adjust the amount of air supplied to the exhaust pipe 200, or may control the open / close state of the electromagnetic valve 170 to the exhaust pipe 200. The amount of air supplied may be adjusted.

The conditions for stopping the supply of secondary air are as follows: when detecting an abnormality in the ignition system, when detecting an abnormality in the fuel injection system, when detecting an abnormality in VVT (Variable Valve Timing) control, when detecting an abnormality in the throttle system, It may be when an abnormality is detected, when an abnormality of the O ₂ sensors 310 and 320 is detected, or the like. When such an abnormality is detected, the supply of secondary air is stopped or the amount of supplied air is limited.

  Further, in the above-described embodiment, the air pump 120 is used to supply air to the exhaust pipe 200. However, air is supplied to the exhaust pipe using negative pressure without using the air pump 120. Also good.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the whole structure containing the control apparatus of the secondary air supply system which concerns on embodiment of this invention. It is a flowchart which shows the control structure of the program performed with the control apparatus of FIG.

Explanation of symbols

10 secondary air supply device, 20 engine, 110 secondary air supply passage, 120 air pump, 130 ASV (air switching valve), 140 reed valve (check valve), 150 pressure sensor, 160 piping, 170 solenoid valve, 200 intake air Pipe, 210 Exhaust pipe, 220 Exhaust purification device, 240 Throttle, 250 Intake filter, 260 Air flow meter, 270 Intake temperature sensor, 280 Engine speed sensor, 310, 320 O ₂ sensor, 1000 Controller, 2000 Engine ECU.

Claims (10)

A control device for a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device of an exhaust system of an internal combustion engine,
Detecting means for detecting a combustion state in the internal combustion engine;
And a control means for controlling the supply of the secondary air based on the detected combustion state. A control device for a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device of an exhaust system of an internal combustion engine,
Detecting means for detecting a combustion state predicted in the internal combustion engine;
And a control means for controlling the supply of the secondary air based on the predicted combustion state.   The control device according to claim 1, wherein the detection unit includes a unit for detecting that the combustion state is unstable.   The control device according to claim 1, wherein the detection unit includes a unit for detecting that the combustion state is unstable based on a rotational speed of the internal combustion engine.   The control device according to claim 4, wherein the detection means includes means for detecting that the combustion state is unstable based on a decrease in the rotational speed of the internal combustion engine.   The control device according to claim 4, wherein the detection means includes means for detecting that the combustion state is unstable based on fluctuations in the rotational speed of the internal combustion engine.   The control device according to claim 2, wherein the detection unit includes a unit for detecting that the predicted combustion state is unstable based on a fuel component supplied to the internal combustion engine.   The control device according to any one of claims 1 to 7, wherein the control means includes means for controlling the supply amount of secondary air to decrease when the combustion state is unstable.   The control device according to any one of claims 1 to 7, wherein the control means includes means for changing a supply amount of secondary air based on a degree of instability of the combustion state. The control device comprises means for detecting an abnormality related to the internal combustion engine;
The control device according to claim 1, further comprising means for controlling the supply of secondary air to be stopped or the supply amount to be reduced when the abnormality is detected.

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